I watched Tom's "Butt Video" in another thread. It's probably one of the best videos to watch. In the video Tom shows how the player's butt travels laterally, or shifts towards the target as the player completes his backswing, pre-setting his weight to make the downswing FAR easier. This is 100% true. But I also think some folks may miss a component that I think is key to replicating that movement.
One thing some folks might miss in the butt video is the player's lead knee position at the top. His lead knee bends forward, and more towards his lead foot. His lead knee moves in that direction because his lead shoulder rotates immediately down on the takeaway. When that occurs it's almost "automatic" that the tailbone/butt will shift towards the target as noted in the video, which pre-sets the hips forward on the downswing.
However, if the takeaway starts with a slight lateral drift of the shoulders, then rotation to the top, the lead knee will want to turn inward (or buckle) toward the trail knee. When that occurs the starting weight of 55/45 changes to 40/60, or the weight distribution reverses to the trail side. Plus, the lead butt will move away from the target. Thus the bottom point of the swing moves to the right side, resulting in topped shots, flips, shanks, hooks, blocks, etc.
A slight lateral drift of the shoulders to start the takeaway can be VERY subtle, nearly undetectable because it's a relic from the shift-and-lift swing that requires an aggressive forward shift of the lower body to start the downswing. On the course I can meander and start drifting my shoulders to start the backswing on the very next shot, but the good news is I know what I did wrong after one bad shot. I don't need to perform a complete swing reassessment. As a round continues I have to concentrate more and more on lead shoulder DOWN on the takeaway because it's easy to get lazy, or get into old habits.
The above movement is very easy to practice without a club and in front of a mirror or reflection. I suggest folding your arms across your chest, get into address position, then do a mock backswing starting with the left shoulder rotating down, and I mean DOWN, then stop at the top and check your lead knee position and weight distribution. You will find the lead knee to be in a similar position to the player in the butt video, and your butt will have shifted forward. It really is almost "too good to be true" automatic.
Then, and even more importantly, practice the incorrect movement, or start the backswing with a two inch lateral shift of the shoulders, then turn to the top and stop. Check your lead knee position and your butt position. The lead knee will have rotated inward, and your butt will have shifted away from the target. Your weight will be on, or even over the outside of your trail foot, and your trail knee will want to bend to support the added weight. Close your eyes and feel both the incorrect and correct weight distributions at the top. Worse, from the incorrect position, as the club reverses direction on the downswing the lead knee will post-up from the inward position and push the lead hip away from the target which throws the club head outward....shank, or massive hook, fat shot, chunk, etc.
On another note, Tom talks about extension upon reaching the top of the backswing. If the shoulders drift to the right, then rotate to the top, it's nearly impossible to achieve any extension at the top because the weight moves onto the trail knee and the trail knee will bend downward to support the added weight (doing the work the lead knee should be doing), and from there the trail knee cannot support the twisting movement to extend. Conversely, when the lead shoulder immediately rotates downward, extension is much easier because the trail knee is not supporting body weight, not bending downward, etc. This can also be an added check in the no club mirror exercise outlined above.
Plus, the narrower the stance, the more chance of a shoulder drift to the right, thus more chance of getting the weight onto, over, or even on the outside of the trail foot. This is why a lot of folks shank short irons, 30 yard wedge shots, etc. The shorter the shot, the MORE critical it becomes to ensure the left shoulder immediately rotates down on the takeaway.
https://saguto.golf/courses/crispier-than-kfc-club-extra-members-only-content-for-youtube/lectures/33761474
I agree with you. Good technical dynamic insights. No Ifs, Ands, or Butts about it.